The North

The North is a mainly mountainous region divided by a number of north-sourh hilly ridges and drains via the Rivers Ping, Wang, Yom and Nan, southward into the Chao Phraya River of Thailand's Central Plains. Small areas in the north of this region drain into the Mae Kong River while parts of the west lie in the watershed of the Salween River. Virtually the whole area lies above 200 m. elevetion, and there are large areas of uplands above 1,000 m. Among the few peaks above 2,000 m is Doi Inthanon, Thailand highest mountain (2,565 m). Average annual rainfall is the lowland varies from 1,000-1,500 mm over most of the region, so that the lower elevetion are dominated chiefly by deciduous forest.

The climax vegetation of the higher mountains (above 1,000 m) is broad-leaved hill evergreen forest. Native pines are also fairly frequent. The area of both lowland and montane forests has been much reduced and most of what remains is heavily this disturbed.

It is in the north that the diversity of montane birds is at its highest, and roughly 50 breeding species appear to be restricted in this region. Babblers, thrushes, and Flycatchers are particularly well represented, both as breeding birds and as migrant visitors and a great many scarce residents or winter visitors are known only from a small number of peaks in the north of this region.

The majority of lowland birds are shared either with those of western or north-eastern Thailand.

There are many special animals in this region such as Eastern Mole, Parti-coloured Flying Squirrel, Long-tailed Goral, Southern Serow, Crocodile Salamander, and etc.

The West is chiefly hilly, extending along the Burmese border, from roughly 16.30' N to 11.40' N. Covering such a great north-south span, the west is an area of great zoogeographical interest, in which northern montane and lowland birds merge with southern lowland forms, including those characteristic of the drier forests of northern Tenasserim as well as a small number of peninsular rainforest species. The mountains are on average lower than those of the North, even though there is one peak over 2000 m, so that there are slightly fewer montane species than in the North.

Much of the area is hot and dry, although rainfall increases further west and south and may be over 2000 mm in some areas fringing the Burmese border. The West is of great conservation importance because it supports the largest remaining expanses of forest and woody secondary growth in Thailand.

North-east Thailand is a dry plateau at 100 to 200 m elevation which drains into the Mekong River which forms its northern and eastern border. To the west, the plateau is bordered by the flat-topped mountains of the Dong Phaya Yen mountain range and to the south, along the border with Cambodia, by the Phanom Dongrak range. The rainfall is mostly very low (less than 1000 mm in some parts of the certre of the region) and highly seasonal, so that most of the area once supported open deciduous woodlands, chiefly dry dipterocarp, and savana, with evergreen forests being mostly confined to the mountain slopes. Some lowland evergreen forest formerly occurred in the extreme north-east bordering the Mekong River, where the rainfall is higher, but has now been almost completely cleared.

The North-east has a long history of intensive human use, and a sophisticated, rice-growing culture may have existed as long as 6,500 years ago, so that all of the lowland forests had probably been altered by man long before the twentieth century.

Today, the North-east supports a higher human population density than any part of the country except the Central Plains. Because of the generally poor soils and low rainfall, a great many people live at subsistance level. Cutting of wood for fuel has removed almost all of the natural cover and such deforestation, together with the hunting of wildlife for food, has resulted in the almost complete disappearance of many lowland birds, including most larger open country species and even many of the small and ecologically tolerant species which would normally inhabit secondary growth. The former distribution patterns of such species will probably never be elucidated. A number of natural and semi-natural wetlands remain, and are of considerable importance for wintering waterfowl.

The most important forests are found on the flanks of the Dong Phaya Yen range, and form a chain of forest patches extending southwards to Khao Yai in the south-west corner of the region and at the western extremity of the Phanom Dongrak range. The mountains are chiefly flat-topped and rise to a maximum elevation of only a little over 1500 m. The northern most mountains, such as Phu Luang (1571 m) appear to have a close affinity with the mountains of Nan province in the northern zoogeographic region with which they share many species and subspecies, and, in fact, were treated by Deignan (1963) as belonging to the North. Progressively fewer montane birds are found southwards towards Khao Yai.

The South-east is a predominantly lowland area, bordered to the south and west by the Gulf of Thailand and to the east by the Cambodian border. A belt of dry lowlands along the Bang Pakong River, which runs east-west, separates this region from the North-east . The rainfall in this region is generally higher than in most other regions of continental Thailand, some parts receiving as much as 3000-4000 mm of rain per year, and hence most of the lowlands were once covered with evergreen forest. The mountains of Khao Soi Dao, an outlier of the Cardamom Mountains of South-west Cambodia, rise to 1670 m elevation.

The bird fauna of the South-east shows a strong affinity with that of the moist rainforest regions of southern Indo-China, and there are many shared subspecies, both among montane and lowland forms. Additionally there are eight subspecies of lowland or submontane forest birds which are thought to be endemic to this region.

The wetter southern part of this region, extending north from the coast towards Ayutthaya and Ang Thong, probably supports most of Thailand's significant breeding colonies of cormorants, herons, and egrets. The larger, more strictly swamp-dwelling birds-such as the Spot-billed Pelican, storks (with the exception of the Asian Openbill) and ibises-have been lost as breeding birds though many species still occur as scarce migrant visitors.

The Central Plains have probably long been a barrier to the dispersal of forest birds and there are many instances where the race of a bird in the lowlands of South-east or North-east Thailand differs from that occurring on the west side. A small number of forest birds until recently inhabited moist woody vegetation in the vicinity of the major rivers in the heart of the Central Plains. Now, the only woodland birds which remain are a few of the more ecologically tolerant species which may still be found in larger orchards, wooded gardens and in the grounds of temples where isolated stands of tall Dipterocarpus alatus trees remain.

The Central Plains supports many winter visitors from the Palearctic. Ducks roost in large concentrarions on a few large water bodies which are protected from disturbance. Many wintering herons, egrets, chats and warblers utilise paddies, other flooded areas, scrub, tall grass and reeds. Although very little mangrove scrub remains around the coast, extensive areas of coastal mudflats extending east and west of Bangkok support large concentrations of wintering and passage shorebirds.

Most of the Thai Peninsula being rather more seasonal than Malaysia, many of the subspecies of lowland forest birds differ and many are endemic to peninsular Thailand or are shared with the extreme south of Burma, which supports a similar, somewhat seasonal, type of rainforest vegetation. About 130 species of Thai birds are confined to the Peninsula and while a small number of these are apparently restricted to the extreme south provinces, the great majority   occur  (or formerly occurred) throughout, extending almost as far as the northern boundary of the region. The lowland bird community lacks only a few peninsular Malaysian species. In addition, there are a few Indo-Chinese species in peninsular Thailand which either do not cross into Malaysia or which are found only in the far north of that country.

One species, Gurney's Pitta, is entirely restricted to peninsular Thailand and extreme southern Burma.There are a number of others, such as the Fulvous-chested Flycatcher, which are found in both peninsular Thailand and Sumatra, but not in the intervening forests of peninsular Malaysia. The forests in the least seasonal, southern

most provinces of Yala and Narathiwat more closely resemble peninsular Malaysian forests in tree species composition and many birds are of the Malaysian, rather than the peninsular Thai, subspecies.

The montane bird fauna is not very rich, since the mountains are very steep and the mountaintop areas very small. None of the endemic, Sundaic montane bird species are known from peninsular Thailand, and relatively few of the mountain bird species found in continental Thailand occur: nonetheless, a number of these (such as the Blue-throated and Golden-throated Barbets; Green-tailed and Black-throated Sunbirds) have diverged into endemic peninsular Thai subspecies.

Almost all of the remaining forest lies on steep hill slopes. A great many lowland rainforest birds, which seem to be wholly or largely confined to the level plains, have therefore disappeared from most of their former range in peninsular Thailand, so that there is probably no single remaining rainforest area which supports a full complement of even the small songbird species. Nevertheless, a few areas of critical conservation importance remain and are protected

Mangrove forests are an important habitat in the Peninsula, the most extensive and species-rich areas occurrisng on the west coast. There are also a great many islands, which are important for such island forest species as Nicobar Pigeon as well as for nesting terns.

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